In many medical emergencies, medical personnel must gain rapid access to the body's vascular system in order to replace fluids and administer medication. This is typically accomplished by attaching a needle to a catheter or syringe, inserting the needle into a vein, and injecting the medical fluids into the bloodstream. However, finding a suitable vein in an emergency can be difficult and time-consuming. For instance, infants and small children may have veins that are barely visible and hard to find. Other problems arise when the patient is an I.V. drug user, and in cases of cardiac arrest, shock, extensive burns, and the like.
Fortunately, access to the vascular system can also be obtained through the bones. With a technique known as intraosseus infusion, an injection device is inserted into the interior of a bone, such as the tibia. Medical fluids are then injected directly into the bone marrow. The fluids flow through the rich vascular network of which the bone marrow is a part, and into the rest of the body.
Although there are a number of existing approaches to intraosseus infusion, the prior known arrangements have significant shortcomings. "Intraosseous Infusions: An Important But Forgotten Method of Vascular Access," by D. D. Von Hoff (Cancer Investigation, 9(5), p. 524 (1991)), suggests an approach using a device that is surgically implanted into the bone. To implant the device, a doctor first cuts through the skin, then drills a pilot hole into the bone, and finally screws the device into the bone at the pilot hole. A needle on the end of intravenous tubing or a syringe is then inserted through the skin into the device. Unfortunately, this surgical approach is poorly suited for use in emergency situations, where time is short and a doctor may not be available.
A simpler method is reported in two other articles, "Emergency Resuscitation In Children: The Role of Intraosseus Infusion," by D. A. Driggers, et al., (Emergency Resuscitation, Vol. 89, No. 4, p. 129 (March 1991)) and "Pediatric Intraosseous Infusion: An Old Technique in Modern Health Care Technology," by C. A. Wheeler (Journal of Intravenous Nursing, Vol. 12, No. 6, p. 371), by which a needle is directly inserted into the bone marrow. Two problems are apparent when this method is used with ordinary medical needles. First, the flexibility of many needles prevents them from penetrating the bone, or at least makes them very difficult to work with. Secondly, the opening at the end of a typical needle is likely to become plugged with bone fragments during insertion, thereby blocking the flow of fluid into the marrow.
Problems arise even when special bone marrow needles are used, such as those disclosed in the Baxter advertisement entitled, "Pharmaseal.RTM. Jamshidi.RTM. and Illinois Sternal/Iliac Bone Marrow Biopsy/Aspiration Needles," and discussed in "Intraosseous Infusion" by D. H. Fiser (New England Journal of Medicine, Vol. 322, No. 22, p. 1579 (May 31, 1990)). Those needles consist of a narrow shaft and a slightly longer stylet with an off-center point at the end. Unfortunately, the needles do not anchor into the bone upon insertion and can be pulled out by accident. Additionally, when a technician rotates the needle to penetrate the bone, the off-center point may cause injury to the overlying skin, muscle, and other tissue of the patient. It should also be noted that none of these needles apply pressure to the skin at the puncture site, and these two negative factors mean that bleeding from the insertion point is likely to occur.
"Evaluation of an Intraosseous Infusion Device for the Resuscitation of Hypovolemic Shock," by L. Halvorsen, et al. (Journal of Trauma, Vol. 30, No. 6, p. 652 (June 1990)), describes a device which includes a shaft with a sharp threaded tip, a knob to rotate the shaft, and a spring mechanism to apply pressure to the skin. A medical technician rotates the shaft tip through the bone and into the marrow. It appears from the Halvorsen drawing and text that medical fluids are infused into the bone marrow through an opening in the sharp tip. A number of drawbacks are apparent in the Halvorsen device. First, the opening in the tip can become clogged during entry into the bone. Second, the narrow diameter of the knob does not appear to be well-suited to generating sufficient torque for easy penetration of the dense outer portion of the bone. Third, the pressure on the skin and flesh generated by the spring cannot be adjusted, which may result in either too much pressure or not enough, depending on variable factors such as the depth of penetration, for example. Additionally, once the threaded tip has fully entered the soft bone marrow, as illustrated in FIG. 2 of the Halvorsen article, there is nothing to securely anchor the device in place.